NEUROPATHIC PAIN IN CHILDREN

Neuropathic pain in children is well documented with an incidence reported to be around 6% (23). While there are some disease processes and causes of neuropathic pain that adults and children share, the picture of neuropathic pain in children is different. Many common causes of neuropathic pain in adults such as diabetes and trigeminal neuralgia are rare in childhood. Disease processes that are common in both include complex regional pain syndrome (CRPS), which will be discussed later, and phantom limb pain. There are multiple known causes of neuropathic pain in children (Table 20A.1) in addition to these, such as Fabry's disease, HIV, and cancer to name a few. Children more frequently, although still rarely, may have neuropathies due to metabolic and toxic causes such as heavy metal positioning or due to neurodegenerative or mitochondrial disorders. Of these, CRPS is likely the most recognized.

TABLE 20A.1 CAUSES OF NEUROPATHIC PAIN IN CHILDREN

Abbreviations: CIDP, chronic inflammatory demyelinating polyneuropathy; CRPS, complex regional pain syndrome.

PHANTOM LIMB PAIN

Children may undergo traumatic or iatrogenic amputation just as their adult counterparts. Children who have undergone surgical amputation of limbs have up to a 40% incidence of phantom limb pain (24). In the pediatric population, it is rarely associated with complications of diabetes of vascular disease, as these disease processes have not been long-standing to lead to amputation. Phantom pain can also occur in children with congenitally missing limbs; however, they are much less likely to experience pain compared to children who lose their limbs later in life (25,26).

Phantom limb pain is children has been described as sharp, stabbing, piercing, squeezing and can lead to significant disability and affect functionality (25).

There are several factors that predispose children to phantom limb pain including older age at the time of amputation, concomitant use of chemotherapy, and preoperative pain. Similar to phantom limb pain is brachial plexus injury.

POSTOPERATIVE AND TRAUMA-RELATED PAIN

The incidence of neuropathic pain in children following surgery is not clear, but is well reported. Common causes of persistent postoperative pain in children are post-thoracotomy pain as well as pain following various orthopedic procedures especially those associated with fracture.

CANCER-RELATED NEUROPATHIC PAIN

The incidence of neuropathic pain in children with cancer is unknown. However, it is known that neuropathic pain in children with cancer can be difficult to treat just as in their adult counterparts. A significant number of children with primary nervous system tumors report neuropathic pain. In addition, chemotherapy is a major cause of neuropathic pain in cancer patients, adult and children alike. Common chemotherapeutics that result in peripheral neuropathy are platinum agents such as cisplatin, and vinca alkaloids such as vincristine and vinblastine.

FABRY'S DISEASE

While Fabry's disease is overall an uncommon cause of neuropathic pain, it merits mention, given it is a disease in which pain is often the presenting symptom and the age of presentation is in the first decade (25,27). Pain is initially intermittent but will generally become constant over time. Fabry's disease is an X-linked recessive disease that leads to accumulation of glycolipids in multiple organs including the central nervous system (CNS). Pain incidence in this disease is quite high with up to 70% of affected males reporting pain (27). Furthermore, treatment of Fabry's disease with enzyme replacement will lead to a decrease in pain scores although it does not decrease the incidence of pain (25).

Although less commonly performed in children than in adults, procedural interventions may be warranted. Procedures such as epidural steroid injections or spinal cord stimulation may be considered in the treatment of children; however, such interventions do not have the same supporting evidence that is present for adults.